High clarity colorless polyesters

ABSTRACT

A polyester which when made into an article such as films, containers, bottles and the like has a very high clarity, a low haze value, and a neutral hue. In the preparation of the resin, an antimony catalyst is utilized along with small amounts of a bluing agent such as a cobalt compound and a phosphate compound with the phosphate compound generally being slightly in excess of an equivalent amount of the cobalt compound. The polyester is made from dicarboxylic acids and preferably aromatic acids such as terephthalic acid reacted with polyhydric alcohols.

CROSS-REFERENCE

This is a continuation application of application Ser. No. 245,838,filed Mar. 20, 1981.

TECHNICAL FIELD

The present invention relates to a polyester which has a high clarity,and is transparent when made into an article. The article has a neutralcolor hue, a low haze value, and no greyness therein.

BACKGROUND ART

Heretofore, numerous compounds and catalysts have been used for thepreparation of polyester resins. However, high clarity, neutral hue, andlow haze polyester articles such as films, sheets, containers, and thelike are desirable, especially for containing food or drink, or whenreplacing glass. Often, antimony has been used as a catalyst, at timesin combination with a phosphite compound. However, the reaction betweenthese two compounds would often result in some amount of antimony metalbeing formed which imparted a gray color to the resin and article formedtherefrom. Moreover, if other catalysts were utilized, a high level ofacetaldehyde was produced which is highly undesirable for use inconnection with food containers.

U.S. Pat. No 3,795,639 to Chimura, et al relates to a process forpreparing linear polyesters wherein the polycondensation of glycolterephthalate is preformed in the presence of (1) an antimony catalyst,(2) a germanium compound and (3) a phosphoric ester. This patent is notpertinent in that it does not utilize a bluing agent and does utilize agermanium compound.

U.S. Pat. No. 3,732,182, to Chimura, et al is not pertinent in that itrelates to a novel antimony compound having the formulaSb(OR₁)(OR₂)(OR₃).

U.S. Pat. No. 3,965,071 to McClelland relates to the preparation ofpolyesters in the presence of a titanium compound, the deactivation of acatalyst by reaction with phosphoric acid or ester and polycondensationin the presence of an antimony compound. Thus this patent relates to acompletely different catalyst system as well as to a deactivation of thetitanium catalyst.

U.S. Pat. No. 3,842,043 relates to a white, transparent polyesterutilizing a polycondensation catalyst solution containing germaniumdioxide, glycol and a solubilizing agent such as calcium, magnesium,strontium and zinc metals or salts thereof. Hence, it is not pertinent.

U.S. Pat. No. 4,082,724 to Hewertson relates to polyesters containing atrihalide or a tri(pseudohalide) of antimony and an organic oxo compoundof phosphorus. The mole ratio of the oxo phosphorus compound to antimonyis generally in excess of 1.0. This patent is not pertinent in that ituses very high amounts of phosphorus compounds and does not utilize abluing agent.

An article of Unitika Co., Plasdoc 31808 V/17 Dewent Publications (April1, 1974), obtains a polyester by polymerizing abis(W-hydroxalkyl)terephthalate and/or its oligomer in the presence ofan antimony compound, a cobalt compound, and a halide phosphatecompound. This article is not pertinent in that a halide phosphatecompound is utilized and relates to making polyesters from dimethylterephthalate.

U.S. Pat. Nos. 3,962,189 to Russin et al, 3,907,754 to Tershansy et al,and 4,010,145 to Russin et al are all very similar in that they relateto catalyst inhibitor systems having a combination of organic orinorganic salts of manganese and cobalt, titanium compounds, antimonycompounds, and a phosphate ester. The amount by weight of phosphorus isgreater than the total weight of cobalt, manganese, and titanium.Moreover, the examples generally show the amount of phosphorus being atleast four times as much as the amount of cobalt. Thus, these referencesare not pertinent in that they use very high amounts of phosphate incomparison to the other metals, as well as use other components notutilized by the present invention. Moreover, they relate to making apolyester from dimethyl terephthalate and not from dicarboxylic acids.

U.S. Pat. No. 2,641,592, to Hofrichter, relates to a cobalt acetatecatalyst in association with antimony for the polymerization of dimethylterephthalate. This patent is not pertinent in that it lacks anysuggestion utilizing any phosphate compound. Additionally, such acomposition would yield unacceptably high acetaldehyde levels incontainers made therefrom.

U.S. Pat. No. 3,028,366 to Engel et al relates to phosphate modifiers inassociation with antimony catalysts to produce colorless or whitepolyesters from dimethyl terephthalate. In passing, the patent statesthat other well known catalysts or catalyst combinations can also beutilized including various metals such as calcium, magnesium, lanthanum,manganese, and cobalt. Since such compounds are utilized as catalysts,high amounts thereof are required. This patent is not pertinent in thatit fails to specifically teach applicant's use of a bluing agent, verysmall amounts of phosphate in comparison with any bluing agent as wellas small amounts of the bluing agent, and relates only to the use ofdimethyl terephthalate.

The above patents and articles all generally relate to the utilizationof dimethyl terephthalate in preparing the polyester. Whenever variouscatalysts are utilized such as manganese, cobalt and the like,relatively high amounts, that is generally in excess of 70 parts permillion by weight of the element must be utilized. Such compoundsnecessarily impart a color to the polyester, for example a blue color,and hence are inherently incapable of producing a neutral hue polyesterartile, that is a colorless or transparent article, with lowacetaldehyde content and generation rate.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention to provide apolyester which yields a high clarity, neutral hue, low haze article.

It is yet another object of the present invention to provide a polyesterwhich yields a high clarity, neutral hue, low haze article, as above,wherein an antimony catalyst, a phosphate compound and a bluing agentare utilized to produce the polyester.

It is yet another object of the present invention to provide a polyesterwhich yields a high clarity, neutral hue, low haze article, as above,wherein said bluing agent is a cobalt compound.

It is yet another object of the present invention to provide a polyesterwhich yields a high clarity, neutral hue, low haze article, as above,wherein said polyester is made from aryl dicarboxylic acids andpolyhydric alcohols.

It is yet another object of the present invention to provide a polyesterwhich yields a high clarity, neutral hue, low haze article, as above,wherein the amount of elemental cobalt compound ranges from about 5parts to about 50 parts per million of polymer, wherein the amount ofelemental phosphorus ranges from about 5 to about 60 parts per millionof polymer and wherein the amount of elemental antimony ranges fromabout 70 to about 250 parts per million of polymer.

It is yet another object of the present invention to provide a polyesterwhith yields a high clarity, neutral hue, low haze article, as above,wherein the polyester is particularly suitable for containers,especially for food containers and particularly bottles, and has lowacetaldehyde levels.

It is yet another object of the present invention to provide a polyesterwhich yields a high clarity, neutral hue, low haze article, as above,wherein a slight molar excess of phosphorus is utilized as compared tothe cobalt.

It is yet another object of the present invention to provide a polyesterwhich yields a high clarity, neutral hue, low haze article, as above,wherein the amount of phosphorus ranges from about 0.35 to about 2.5parts by weight per one part of elemental cobalt.

It is yet another object of the present invention to provide a polyesterwhith yields a high clarity, neutral hue, low haze article, as above,wherein the cobalt is added to the polymerization process before theantimony is added.

These and other objects of the present invention will become apparentfrom the following description of the invention.

Generally, a polyester which yields a high clarity, low haze, neutralhue article comprises: the polyester containing from about 70 to about250 parts by weight of elemental antimony per 1 million parts of saidpolyester; a low amount by weight of a phosphorus compound and a bluingagent, the amount of said phosphorus compound ranging from about 0.35 to2.5 parts by weight for each part by weight of a metal in said bluingagent.

Generally, the process for making a polyester article having a highclarity, low haze, neutral hue comprises the steps of: preparing apolyester resin, adding a small amount of phosphorus and a bluing agent,wherein the amount of phosphorus to metal in said bluing agent rangesfrom about 0.35 to about 2.5 parts by weight, and adding from about 70to about 250 parts by weight of elemental antimony in the form of anantimony compound to said polyester during the preparation thereof.

BEST MODE FOR CARRYING OUT THE INVENTION

High clarity polyesters are produced utilizing an antimony catalyst andlow amounts of phosphorus and a bluing agent. By the term "bluing agent"as utilized in the present invention, it is meant any compound whichupon addition to the polymer during preparation thereof will act as ablue colored compound or pigment and neutralize any otherwise yellowcolor in the polyester formed to yield a transparent, colorless orneutral hue article. In other words, the bluing agent, although often ablue colored compound, can be a red compound such as cobalt acetate, agreen compound, or the like, which upon addition to the polymerizationprocess reacts and forms a blue colored compound which neutralizesyellow and forms a transparent polyester when made into an article. Thepolyesters when made into articles have very high clarity, neutral hue,low haze, and low acetaldehyde levels and thus are suitable as films,sheets, or in any other form when a bright high clarity with low haze isdesired. Particularly suited articles include containers, especially forfoods, and bottles.

The polyester resin is produced in a conventional manner but only fromthe reaction of dicarboxylic acids having from from 2 to about 16 carbonatoms with polyhydric alcohols such as glycols or diols containing from2 to about 12 carbon atoms. The alkyl dicarboxylic acids may contain atotal of from 2 to 16 carbon atoms. Preferably, the acids are aryl or analkyl substituted aryl acid containing from 8 to 16 carbon atoms.Specific examples of linear or alkyl dicarboxylic acids include oxalicacid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelicacid, suberic acid, azelaic acid, sebacic acid, and the like. Specificexamples of an aryl acid include the various isomers of phthalic acid,such as paraphthalic acid (terephthalic acid) and naphthalic acid.Specific examples of alkyl substituted aryl acids include the variousisomers of dimethylphthalic acid such as dimethylisophthalic acid,dimethylorthophthalic acid, dimethylterephthalic acid, the variousisomers of diethylphthalic acid such as diethylisophthalic acid,diethylorthophthalic acid, diethylterephthalic acid, the various isomersof dimethylnaphthalic acid such as 2,6-dimethylnaphthalic acid and2,5-dimethylnaphthalic acid, and the various isomers ofdiethylnaphthalic acid. Generally, terephthalic acid is highlypreferred.

Polyesters made from diesters such as dimethylterephthalate do not formany part of the present invention. When such a monomer is utilized, highamounts of catalyst, that is generally the 70 parts per million of theelemental catalyst, are required in order to promote the esterificationand condensation reactions. Such amounts of catalyst are in excess ofthe present invention and will impart a color to the polyester andarticles formed therefrom. The present invention completely avoids anycolor hue by utilizing the dicarboxylic acids and hence, utilizes lowamounts of cobalt, that is generally less than 50 parts per million, anddesirably less than 30 parts per million.

The diols or glycols may be straight chained or branched. Specificexamples include ethylene glycol, propylene glycol, trimethylene glycol,1,2-butane diol, 1,3-butane diol, 1,4-butane diol, 2,3-butane diol,neopentyl glycol, and the like. Of the various glycols, those havingfrom 2 to 8 carbon atoms are preferred with ethylene glycol and1,4-butane diole being highly preferred. In lieu of the various glycols,another class of polyhydric alcohols, such as the glycol etherscontaining from 4 to 12 carbon atoms, can be utilized as for exampledimethylene glycol and 1,4-dihydroxyethoxy benzene.

The polyesters can be made according to melt polymerization, or melt andsolid state polymerization. As known to those skilled in the art,polyesters are generally made in two stages. In the first stage oresterification stage, the diacid is reacted with the diol at elevatedtemperatures and pressures with water being produced. In the secondstage or the polycondensation stage, a vacuum is gradually applied, orgenerally catalysts are utilized, and water and a diol are withdrawn asa condensation product. Various polyesters can be made by such apolymerization including polyethyleneterephthalate, a preferredpolyester resin. Moreover, the process may be modified slightly byreacting the dicarboxylic acid with the diol in a solvent which is a lowmolecular weight linear polyester in a manner as set forth in U.S. Pat.No. 4,020,049 to Rinehart which is hereby fully incorporated with regardto the method of making the polyester resin. That is, the dicarboxylicacid and the glycol added in a molar ratio of the glycol to the acid offrom 1.7:1 to 1.05:1 to a solvent consisting of a preformed lowmolecular weight condensation polyester of a glycol and a dicarboxylicacid, the polyester having an average degree of polymerization of from1.4 to 10. The mixture is then heated and reacted at a temperature atleast from above the melting temperature of the low molecular weightlinear polyester to a temperature of 300° C. with the pressure beingfrom about 20 to about 1,000 pounds per square inch gauge. The reactionis continued until a linear condensation polyester resin made from saidglycol and said acid, having an average degree of polymerization of from1.4 to 10, is produced. The condensation or polymerization reaction iscarried out until a linear polyester is formed at elevated temperatureunder reduced pressure, that is approximately 10 millimeters or less ofmercury. The condensation reaction temperature is from about 260° toabout 290° C. Regardless of the exact process, such reactions can becarried out in situ.

Solid state polymerization can also be utilized. In this process, thepolycondensation reaction is carried out until generally the intrinsicviscosity of the polymer melt reaches about 0.20 or higher, for example,up to about 0.80. At this point, the solution melt is cooled to producea solid which is then pelletized, chopped, etc. The pellets are thensubjected to a solid state polymerization wherein the vacuum is appliedat a temperature below the melting point of the partially formedpolymer. Alternatively, the polymerization can be accomplished byremoval of the by-product, e.g. water, ethylene glycol, by circulatingor blowing an inert gas through the pellets. Thus, the polymer isactually polymerized in a solid state, with the polycondensationreaction being conducted in such a state. Generally, the solid statepolymerization is continued until the intrinsic viscosity reaches anydesirable level, such as from about 0.60 to about 1.0, or even higher.That is, at times it is desirable to produce very high molecular weightpolyesters, for example, a polyester having an intrinsic viscosity offrom about 1.0 to about 1.2. Desirably, the intrinsic viscosity rangesfrom about 0.70 to about 0.85 and preferably from about 0.70 to about0.80. By intrinsic viscosity it is meant that the value obtained whenn_(specific) /C or LOG r_(rel). /C is extrapolated to zeroconcentration; where the relative viscosity is defined as the quotientof the solution viscosity, n_(soln). and the viscosity of the solventn_(solv)., i.e., n_(rel). =n_(soln). /n_(solv). The specific viscosityn_(sp). =n_(rel). -1. The units are deciliters/gram using a 60/40phenol/tetrachloroethane at 25° C. The symbol n is for the Greek lettereta.

When the polyester resin is intended for use in contact with food onlythose polyesters which are regulated by the Federal Food and DrugAdministration should be utilized, such as set forth in Title 21,§177.1630, for example, the polyethylenephthalate polymers, and suchpolysters are preferred in the present invention.

The antimony catalyst utilized in the present invention can be generallyany trivalent organic antimony compound known to the art. Examples ofspecific antimony compounds include antimony triacetate, antimonytrioxide, antimony glycolate (either formed separately or duringpolymerization), and the like, with antimony glycolate being preferred.The antimony compound desirably is added to the condensation stage orstep of the polymerization.

The present invention also relates to the use of relatively low amountsof a phosphorus compound, for example a phosphate, and a bluing agent incomparison to the weight or amount of the antimony catalyst. The term"phosphate" as utilized in the present invention includes variousphosphate compounds known in the art as well as phosphoric acid. Thebluing agents are generally cobalt compounds which may or may notinitially be blue as previously discussed. The polyester resins of thepresent invention can be made to form various articles such as films,sheets, containers, and the like. The some of these applications whereinthe polyester is utilized as a container, for example, for containingcarbonated beverages, it is highly desirable to maintain or to have lowacetaldehyde levels to prevent discernible differences in taste. Forexample, the addition of levels of acetaldehyde as low as 60 parts perbillion by weight have altered the tastes of carbonated cola beverages.Other food stuffs have different taste threshold levels which may beexceeded if the acetaldehyde level is not minimized. Desirably, when acontainer is utilized to contain food stuffs or liquids such asbeverages, the amount of acetaldehyde diffusing from the container walls(e.g., a 2 liter bottle) of an empty, freshly blown bottle is less than3 micrograms per liter. This test is conducted by maintaining thecontainer at 70° F. for twenty-four hours, and then testing the gasescontent therein to determine the amount by weight of acetaldehyde.Generally it has been found that wherein the acetaldehyde content isless than 3 micrograms per liter of volume in a container withintwenty-four hours after preparation thereof, any remaining accumulationof acetaldehyde is low and presents no discernible taste in a beverage,food stuff, or the like with longer periods of storage.

Since cobalt compounds have been shown to increase the acetaldehydelevel in a container, an amount of a phosphate compound (includingphosphoric acid) is utilized to suppress the catalytic activity of thecobalt compound. Generally, one part by weight of elemental cobaltrequires approximately 0.35 parts by weight of elemental phosphorus.Preferably, a slight excess of the phosphorus compound is utilized toinsure suppression of the catalytic influence of the cobalt compound onacetaldehyde production. Thus, according to the present invention, fromabout 0.35 to about 2.5 parts by weight and preferably from about 0.4 toabout 0.6 parts by weight of elemental phosphorus is desired for everyone part of elemental cobalt. Should a greater amount be utilized, freephosphate will generally exist which will react with the antimony toproduce an antimony phosphate type compound and if sufficient amountsexist in excess of the solubility limit of such a compound, will formparticles and/or nucleation of crystallinity upon formation of thepolyester. This results in a hazed article.

The present invention as noted above relates to the article when formedfrom a polyester resin has low haze, a neutral color, and high clarity.If a bluing agent is not utilized, the resulting polymer produced wouldgenerally not have the neutral hue in that it would have an undesirableyellowish tinge or color.

Desirably, from about 70 to about 250 parts by weight per million ofelemental antimony is desired based upon the produced polyester resinwith the preferred range being from about 120 to about 210 parts permillion. The amount of cobalt ranges from about 5 parts to about 50parts by weight per million, desirably from about 5 to about 30 parts,and preferably from about 8 parts to about 20 parts per million. Theamount of the phosphate compound expressed in terms of elementalphosphorus per million parts of polyester polymer ranges from about 5 toabout 60 parts, desirably from about 10 to about 50 parts, andpreferably from about 8 to about 20 parts by weight. Typical cobaltcoloring agents include cobalt acetate tetrahydrate, cobalt aluminate,cobalt benzoate, cobalt chloride, and the like with cobalt acetate beingpreferred. Examples of typical phosphate compounds include anypentavalent phosphates such as phosphoric acid, trialkylphosphates, forexample, trimethylphosphate, triethylphosphate, tripentylphosphate, andthe like. Triaryl phosphates such as triphenyl phosphate, triarylphosphate, and the like can also be utilized. Additionally, mono anddialkyl/aryl phosphates may be utilized. Phosphoric acid and thetrialkyl phosphates are preferred.

Desirably, the phosphate and the cobalt compounds are added before theantimony addition, and preferably during the beginning of theesterification stage although they can be added at the beginning of thecondensation stage. The preparation of the polyester resin can beconducted in any conventional manner utilizing a dicarboxylic acid. Thatis, conventional temperatures, pressures, reaction times, and the likeare utilized as well known to those skilled in the art.

The articles made from polyester resins of the present invention exhibitvery high clarity, low haze values, and neutral hue. The haze value isgenerally indicated by a haze number according to the Hunter haze test.The haze number is generally less than 3.0, desirably less than 2.5, andpreferably less than 2.0. Often, haze values are measured by eyesightsince they tend to be more accurate than the Hunter values. The neutralhue is generally indicated by utilizing a Hunter Lab instrument.Generally, the hue is neutral as indicated by an "a" coordinate valueranging from about -1.0 to about 1.0, and preferably from about -0.5 toabout 1.0, and a "b" coordinate value ranging from about -2.0 to about2.0, and preferably from about -0.5 to about 2.0. That is, the numbersare basically on the zero-zero coordinates which indicates that theresulting article, for example a beverage bottle has no color.

The invention will be better understood by reference to the followingexamples.

POLYESTER REACTOR PROCESSING EXAMPLE

The poly(ethylene terephthalate) polyesters described in Table III wereprepared in a 200 pound polyester process reactor. The materials chargedto the reactor, identification, amounts and points of addition, areshown in Table IA. The processing conditions and procedures for theesterification (S/1) reaction are shown in Table IB, and the same forthe polycondensation (S/2 and S/3) reactions are shown in Table IC.

                                      TABLE I                                     __________________________________________________________________________    Polyester Reactor Processing                                                  0.60 ± 0.02 I.V. Feed Polymer                                              __________________________________________________________________________    A. Raw Materials     Amount                                                   Raw Material %  S/   (lbs.)                                                                            (gms.) Active Element.                                                                        ppt                                  __________________________________________________________________________    Terephthalic acid (TPA)                                                                    100                                                                              1    129.0                                                                             --     --       --                                   Ethylene glycol (EG)                                                                       100                                                                              1    50.7                                                                              --     --       -                                    H.sub.3 PO.sub.4 :EG.sup.a                                                                 -- 1    --  102.1  P        0.015                                Co(C.sub.2 H.sub.3 O.sub.2).sub.2.4H.sub.2 O:EG.sup.a                                      -- 2    --  215.3  Co       0.015                                Sb.sub.2 O.sub.3 :EG.sup.b                                                                 -- 2    --  285.5  Sb       0.130                                Ethylene glycol makeup                                                                     -- 2    16.8                                                                              --     --       --                                   __________________________________________________________________________    B. Esterification (S/1) Reaction Conditions and Procedures                    Elasped Time                                                                         Batch  Oil    Pressure                                                                            Head                                               (Min.) Temp., °C.                                                                    Temp., °C.                                                                    PSI   Temp., °C.                                                                    Procedure                                   __________________________________________________________________________     0     260    267    10    108    charge TPA                                   5     226    257    40    107    charge H.sub.3 PO.sub.4 :EG, EG             48     256    283    70    129                                                60     260    288    70    130    start temp. program                         135    284    291    10    108    transfer to S/2 vessel                      __________________________________________________________________________    C. Polycondensation (S/2 and S/3) Reaction Conditions and Procedures          Elasped Time                                                                          Batch Oil   Pressure                                                                            Agitator                                            (Min.)  Temp., °C.                                                                   Temp., °C.                                                                   mm of Hg                                                                            RPM  Procedure                                      __________________________________________________________________________         142                                                                              280   285   Atm.  --   charge Co(C.sub.2 H.sub.3 O.sub.2).sub.2.4                                    H.sub.2 O:EG                                        147                                                                              262   285   Atm.  --   charge Sb.sub.2 O.sub.3 :EG, start             S/2                            vacuum                                              152                                                                              274   285   100   --                                                       193                                                                              275   286   2.5   --   transfer to S/3 vessel                              196                                                                              273   283   300   73                                                  S/3  208                                                                              281   286   0.30  66                                                       242                                                                              283   286   0.15  30   cut vacuum and pressurize                                                     to 8 PSI to extrude resin                                                     ribbon that is diced into                                                     1/8 inch cubes.                                     260                       end of dicing                                  __________________________________________________________________________     .sup.a Raw materials dissolved in ethylene glycol                             .sup.b Sb.sub.2 O.sub.3 reacted with EG to yield Sb glycolate                 The 0.60 ± 0.021 I.V. feed resin is subsequently solid state               polymerized to 0.72 ± 0.02 IV in a 3 ft.sup.3 blenderdryer reaction        vessel using conditions and procedures outlined in Table II.             

                  TABLE II                                                        ______________________________________                                        Polyester Solid State Polymerization 3 ft.sup.3                               Blender-Dryer 0.72 ± 0.02 I.V.                                             Elasped Oil     Batch                                                         Time    Temp.,  Temp.,                                                        (hrs.)  °C.                                                                            °C.                                                                             Procedure                                            ______________________________________                                        0       190     --       Charge 100 pounds of feed resin                      1.5     190     150      Crystallize at atm. pressure                         8.0     237     226      Solid state polymerize at                                                     0.2-.3 mm of Hg vac.                                 10.0    --      --       Cool resin temp. to 40-50° C.                                          and discharge                                        ______________________________________                                    

                                      TABLE III                                   __________________________________________________________________________    Improved Appearance PET Properties                                            __________________________________________________________________________                Feed Resin Properties                                             Composition,                                                                  ppm                                 Gardner Color                             Sample                                                                            Sb Co                                                                              P  I.V., dl/gm                                                                         COOH.sup.Eq/ 10.sup.6 gms                                                              Mettler M.P., °C.                                                               Rd a  b   CH.sub.3 CHO Content,           __________________________________________________________________________                                                  ppm                             1   210                                                                              --                                                                               25*                                                                             0.606 17       255.1    24.0                                                                             -0.5                                                                             2.4 51.5                            2   150                                                                              --                                                                              -- 0.568 22       255.8    40.0                                                                             -1.2                                                                             8.9 56.9                            3   150                                                                              50                                                                              -- 0.561 27       256.0    20.9                                                                              5.4                                                                             -8.5                                                                              80.7                            4   150                                                                              50                                                                              40 0.574 14       255.5    32.1                                                                             -0.1                                                                             -0.3                                                                              51.9                            5   130                                                                              15                                                                              15 0.572 17       254.4    30.7                                                                              0.6                                                                             0.1 52.0                                        Solid State Resin Properties                                      1   Same as Above                                                                         0.709 12       --       53.4                                                                             -2.0                                                                             0.0 1.6                             2   "       0.715 15       --       73.1                                                                             -2.4                                                                             11.9                                                                              1.1                             3   "       0.713 18       --       48.3                                                                              1.5                                                                             -6.1                                                                              1.7                             4   "       0.747  9       --       61.0                                                                             -1.4                                                                             -1.3                                                                              1.2                             5   "       0.716 12       --       66.3                                                                             -1.4                                                                             -1.1                                                                              1.4                                         CH.sub.3 CHO Generation Rate (ppm/min.)                           1   Same as Above                                                                         1.12                                                              2   "       1.13                                                              3   "       3.36                                                              4   "       1.23                                                              5   "       1.16                                                              __________________________________________________________________________                BOTTLE PREFORM PROPERTIES                                                     Hunter Values                                                                 L                    (a) (b)                                      __________________________________________________________________________    1   Same as Above                                                                         56.2                 -2.1                                                                              3.6                                      2   "       71.4                 -2.8                                                                              7.1                                      3   "       64.3                 1.0 0.8                                      4   "       68.7                 0.8 2.2                                      5   "       71.8                 1.0 2.0                                      __________________________________________________________________________                        Bottle Properties (2 Liter)                               Composition, ppm    Hunter                                                                            Sidewall       Headspace CH.sub.3 CHO Content         Sample                                                                            Sb    Co P      L   a     b Haze   Visual    μg/l                      __________________________________________________________________________                                                     (ppb)                        1   210   --  25*   86.9                                                                              -0.8  1.7                                                                             3.4    Bottle hazy and                                                                         2.2                                                                 reduced brightness                     2   150   -- --     88.7                                                                              -0.8  1.9                                                                             1.7    Yellow neck and                                                                         2.6                                                                 bottom                                 3   150   50 --     88.2                                                                                0.0 1.3                                                                             1.7    Bluish tinge                                                                            10.2                                                                neck and bottom                        4   150   50 40     88.0                                                                              +0.2  1.4                                                                             3.6    Clear neck and                                                                          2.0                                                                 bottom                                 5   130   15 15     88.9                                                                              -0.2  1.3                                                                             1.7    Clear neck and                                                                          2.1                                                                 bottom                                 __________________________________________________________________________     *Phosphite                                                               

As previously noted, the present invention relates to a polyester whichproduces an article having a high clarity, a low haze, and neutral hue.Examining Table III, the data sets forth clarity, haze values, and colorvalues, that is neutral hue; with regard to Example I, a prior artpolyester containing antimony and a phosphite; Example II relates to apolyester produced merely containing antimony; Example III relates to apolyester produced containing only antimony and cobalt; whereas ExamplesIV and V relate to the present invention. As apparent from the variousdata such as the feed resins and solid state resin properties, the priorart resin has a reduced brightness value. Example II has yellow resin,whereas Example III has bluish resin and a reduced brightness. However,Examples IV and V have a neutral color as well as good brightness.Concerning the preform properties, that is an item made from a resinsuch as a parison, the prior art article has reduced brightness; ExampleII has a yellow color; and Example III has a reduced brightness.However, Example IV and V have good brightness and therefore clarity anda neutral hue. Examining now the bottle properties which are takenthrough the sidewall, it is seen that Example I does show a fair amountof haze. The visual inspection also reveals that the bottle is hazy andhas reduced brightness. Although Examples II and III show clear Huntersidewall values, the visual inspection reveals that the neck and bottomwhich tend to be thicker are yellow and blue, respectively. Thus, theydo not contain a neutral hue. Moreover, Example III which contains thecobalt, has an unacceptable amount of acetaldehyde content. In contrast,Examples IV and V, both through the instrument readings and visualreadings, have clear bottles including the neck and bottom portion andhave no haze. The clarity is high and the acetaldehyde levels are low.Thus, it is apparent that the present invention yields a high claritybright bottle having low haze and a neutral or no color thereto.

While having described the best mode as well as the preferred embodimentof the present invention, in accordance with the patent statutes, it isnoted that the invention is not limited thereto, the scope of theinvention being measured by the attached claims.

What is claimed is: .[.
 1. A polyester, comprising:a polyester resin,said polyester resin made solely by adding a dicarboxylic acid to aglycol compound in a molar ratio of said alcohol to said acid of from1.7:1 to 1.05:1, said dicarboxylic acid selected from the groupconsisting of alkyl dicarboxylic acids having a total of from 2 to 16carbon atoms, aryl or alkyl substituted aryl dicarboxylic acidscontaining a total of from 8 to 16 carbon atoms, and combinationsthereof, and wherein said glycol is selected from the group consistingof glycols having from 2 to 12 carbon atoms, glycol ethers having from 4to 12 carbon atoms, and combinations thereof, forming a mixture byadding a phosphorus compound, a cobalt compound as well as said alcoholand said acid to a solvent consisting of a preformed molecular weightlinear condensation polyester of a glycol and a dicarboxylic acid, saidpolyester having an average degree of polymerization of from 1.4 to 10,heating and reacting the mixture at a temperature from above the meltingtemperature of a low molecular weight linear polyester to 300° C. at apressure of from about 20 to about 1000 pounds per square inch gaugepressure until a linear condensation polyester resin of said glycol andacid having an average degree of polymerization of from 1.4 to 10 isformed, adding a condensation antimony polymerization catalyst and thenheating and reacting the mixture at a temperature of from about 260° C.to about 290° C. at a pressure of about ten millimeter of mercury orless until a linear polyester is formed, said polyester consistingessentially of said antimony compound, said phosphorus compound, andsaid cobalt compound, the amount of said antimony compound, based uponthe amount of elemental antimony therein, ranging from about 70 to about250 parts by weight per one million parts by weight of said polyester,the amount of said phosphorus compound, based upon the amount ofelemental phosphorus therein, ranging from about 5 to about 60 parts byweight per million parts by weight of said polyester, the amount of saidcobalt compound based upon the amount of elemental cobalt thereinranging from about 5 to about 50 parts by weight per million parts byweight of said polyester, the amount of said elemental phosphorus insaid phosphorus compound ranging from about 0.35 to about 2.5 parts byweight for each part by weight of elemental cobalt in said cobaltcompound, said polyster resin yielding a high clarity, low haze, neutralhue article having a haze value of less than 3.0..]. .[.
 2. A polyesteraccording to claim 1, wherein said phosphorus compound is aphosphate..]. .[.3. A polyester according to claim 2, having a hazevalue of less than 2.5, wherein the amount of elemental cobalt in saidcobalt compound ranges from about 5 to about 30 parts by weight permillion parts by weight of said polyester, wherein the amount of saidelemental phosphorus in said phosphorus compound ranges from about 10 toabout 50 parts by weight per million parts by weight of said polyester,and wherein the ratio of said elemental phosphorus to said elementalcobalt ranges from about 0.4 to about 1.3 parts by weight..]. .[.4. Apolyester according to claim 3, wherein said neutral hue, high clarity,low haze article consists essentially of said polyester resin, saidantimony compound, said phosphorus compound, and said cobaltcompound..]. .[.5. A polyester according to claim 4, wherein said cobaltcompound is cobalt acetate, wherein said phosphorus compound isphosphoric acid, and wherein said antimony compound is antimonyglycolate..]. .[.6. A polyester according to claim 5, wherein saiddicarboxylic acid is a terephthalic acid, and wherein said glycol isethylene glycol, and wherein said polyester has a Hunter "a" coordinatevalue of from about minus 1.0 to about 1.0 and a "b" coordinate value offrom about minus 2.0 to about 2.0..]. .[.7. A polyester according toclaim 3, wherein said polyester is in the form of a container..]. .[.8.A polyester according to claim 6, wherein said polyester is in the formof a container and wherein the amount of elemental antimony in saidantimony compound ranges from about 120 to about 210 parts of antimonyper million parts by weight of said polyester, and wherein the amount ofsaid elemental cobalt in said cobalt compound ranges from about 8 toabout 20 parts by weight per million parts by weight of saidpolyester..]. .[.9. A polyester according to claim 7, wherein saidcontainer is a bottle..].
 10. A process for making a polyester,.Iadd.which is suitable for utilization in making articles having highclarity, low haze and neutral hue, .Iaddend.comprising the stepsof:preparing a .[.polyester resin,.]. .Iadd.preformed low molecularweight linear condensation polyester.Iaddend., said .[.polyesterresin.]. .Iadd.preformed low molecular weight linear condensationpolyester .Iaddend.made solely by .[.adding .]. .Iadd.reacting.Iaddend.a dicarboxylic acid .[.to.]. .Iadd.with .Iaddend.a glycolcompound .[.in a molar ratio of said glycol to said acid of from 1.7:1to 1.05:1, said dicarboxylic acid selected from the group consisting ofalkyl dicarboxylic acids having a total of from 2 to 16 carbon atoms,aryl or alkyl substituted aryl dicarboxylic acids containing a total offrom 8 to 16 carbon atoms, and combinations thereof, and wherein saidglycol is selected from the group consisting of glycols having from 2 to12 carbon atoms, glycol ethers having from 4 to 12 carbon atoms, andcombinations thereof.].; forming a mixture by adding .[.said glycol andsaid.]. .Iadd.a glycol and a dicarboxylic .Iaddend.acid .Iadd.in a molarratio of said glycol to said acid of from 1.7:1 to 1.05:1, said acidselected from the group consisting of alkyl dicarboxylic acids having atotal of from 2 to 16 carbon atoms, aryl or alkyl substituted aryldicarboxylic acids containing a total of from 8 to 16 carbon atoms, andcombinations therefor, and wherein said glycol is selected from thegroup consisting of glycols having from 2 to 12 carbon atoms, glycolethers having from 4 to 12 carbon atoms, and combinations thereof.Iaddend.to a solvent consisting of .[.a.]. .Iadd.said.Iaddend.preformed low molecular weight linear condensation .[.polyesterof a glycol and a dicarboxylic acid.]., said .Iadd.preformed lowmolecular weight linear condensation .Iaddend.polyester having anaverage degree of polymerization of from 1.4 to 10, heating and reactingthe mixture at a temperature from above the melting temperature of the.Iadd.preformed .Iaddend.low molecular weight linear .Iadd.condensation.Iaddend.polyester to 300° C. at a pressure of from about 20 to about1000 pounds per square inch gauge pressure until a linear condensationpolyester resin of said glycol and .Iadd.said dicarboxylic .Iaddend.acidhaving an average degree of polymerization of from 1.4 to 10 is formed;.[.adding a condensation antimony polymerization catalyst.]. and thenheating and reacting the mixture at a temperature of from about 260° C.to about 290° C. at a pressure of about ten millimeter of mercury orless until a linear polyester is formed; adding during preparation ofsaid linear condensation polyester resin compounds consistingessentially of a phosphorus compound, and a cobalt compound, addingduring preparation of said linear polyester .[.polymer.]. an antimony.[.compound.]. .Iadd.polymerization catalyst .Iaddend.the amount of saidantimony .[.compound.]. .Iadd.polymerization catalyst .Iaddend.basedupon the amount of elemental antimony therein ranging from about .[.70.Iadd.80 .Iaddend.parts to about 250 parts by weight per one millionparts by weight of said polyester, the amount of said phosphoruscompound based upon the amount of elemental phosphorus therein rangingfrom about 5 to about .[.60 .Iadd.50 .Iaddend.parts by weight permillion parts by weight of said polyester, the amount of said cobaltcompound based upon the amount of elemental cobalt therein ranging fromabout 5 to about 50 parts by weight per one million parts by weight ofsaid polyester; wherein the amount of elemental phosphorus in saidphosphorus compound to elemental cobalt in said cobalt compound rangesfrom about 0.35 to about 2.5 parts by weight.[.; and said polyesterhaving a haze value of less than 3.0, high clarity, and neutral hue whenmade into an article.]..
 11. A process according to claim 10, includingadding said cobalt compound before the step of adding said antimonycompound.
 12. A process according to claim 11, wherein said phosphoruscompound is a phosphate.[., and wherein said article has a haze value ofless than 2.5.]..
 13. A process according to claim 12 wherein the amountof elemental cobalt in said cobalt compound ranges from about 5 parts toabout 30 parts per million parts of said polyester, wherein the amountof elemental phosphorus in said phosphorus compound ranges from about 10parts to about 50 parts per million parts of said polyester, and whereinthe ratio of said elemental phosphorus to said elemental cobalt rangesfrom about 0.4 to about 1.3 parts by weight.
 14. A process according toclaim 13, wherein said cobalt compound is cobalt acetate, wherein saidphosphorus compound is phosphoric acid, and wherein said antimonycompound is antimony glycolate.
 15. A process according to claim 14,wherein said dicarboxylic acid is terephthalic acid, and wherein saidglycol is ethylene glycol.[., and wherein said polyester has a Hunter"a" coordinate value of from about minus 1.0 to about 1.0 and a "b"coordinate value of from about minus 2.0 to about 2.0.]..
 16. A processaccording to claim 15, wherein said polyester is prepared utilizing anesterification stage and a condensation stage, and including adding saidphosphorus compound at said esterification stage, and said antimonycompound at said condensation stage.
 17. A process according to claim13, including forming said polyester into a container.
 18. A processaccording to claim 16, including forming said polyester into acontainer, and wherein the amount of elemental antimony in said antimonycompound ranges from about 120 to about 210 parts of antimony permillion parts by weight of said polyester, and wherein the amount ofsaid elemental cobalt in said cobalt compound ranges from about 8 toabout 20 parts by weight per million parts by weight of said polyester.19. A process according to claim 17, wherein said container is a bottle..Iadd.20. The polyester made by the process specified in claim10..Iaddend. .Iadd.21. The polyester made by the process specified inclaim 15..Iaddend. .Iadd.22. A process according to claim 10, whereinsaid dicarboxylic acid is terephthalic acid, and wherein said glycol isethylene glycol..Iaddend. .Iadd.23. A process for making a polyester,comprising:forming a mixture by adding a glycol and a dicarboxylic acidto a solvent consisting of a preformed low molecular weight linearcondensation polyester, said preformed low molecular weight linearcondensation polyester having an average degree of polymerization offrom 1.4 to 10, heating and reacting the mixture at a temperature fromabove the melting temperature of the preformed low molecular weightlinear condensation polyester to 300° C. at a pressure of from about 20to about 1000 gauge pounds per square inch until a linear condensationpolyester resin of said glycol and said dicarboxylic acid having anaverage degree of polymerization of from 1.4 to 10 is formed; and thenheating and reacting the mixture at a temperature of from about 260° C.to about 290° C. at a pressure of about ten millimeter of mercury orless until a linear polyester is formed; wherein said dicarboxylic acidis selected from the group consisting of alkyl dicarboxylic acidscontaining from 2 to 16 carbon atoms, aryl or alkyl substituted aryldicarboxylic acids containing from 8 to 16 carbon atoms, andcombinations thereof; and wherein said glycol is selected from the groupconsisting of glycols containing from 2 to 12 carbon atoms, glycolethers containing from 4 to 12 carbon atoms, and combinations thereof;adding during preparation of said linear condensation polyester resincompounds consisting essentially of a phosphorus compound, and a cobaltcompound, adding during preparation of said linear polyester an antimonypolymerization catalyst the amount of said antimony polymerizationcatalyst based upon the amount of elemental antimony therein rangingfrom about 70 parts to about 250 parts by weight per one million partsby weight of said polyester, the amount of said phosphorus compoundbased upon the amount of elemental phosphorus therein ranging from about5 to about 60 parts by weight per million parts by weight of saidpolyester, the amount of said cobalt compound based upon the amount ofelemental cobalt therein ranging from about 5 to about 50 parts byweight per one million parts by weight of said polyester; wherein theamount of elemental phosphorus in said phosphorus compound to elementalcobalt in said cobalt compound ranges from about 0.35 to about 2.5 partsby weight..Iaddend. .Iadd.24. A process according to claim 23, includingadding said cobalt compound before the step of adding said antimonycompound..Iaddend. .Iadd.25. A process according to claim 24, whereinsaid phosphorus compound is a phosphate..Iaddend. .Iadd.26. A processaccording to claim 25 wherein the amount of elemental cobalt in saidcobalt compound ranges from about 5 parts to about 30 parts per millionparts of said polyester, wherein the amount of elemental phosphorus insaid phosphorus compound ranges from about 10 parts to about 50 partsper million parts of said polyester, and wherein the ratio of saidelemental phosphorus to said elemental cobalt ranges from about 0.4 toabout 1.3 parts by weight..Iaddend. .Iadd.27. A process according toclaim 26, wherein said cobalt compound is cobalt acetate, wherein saidphosphorus compound is phosphoric acid, and wherein said antimonycompound is antimony glycolate..Iaddend. .Iadd.28. A process accordingto claim 27, wherein said dicarboxylic acid is terephthalic acid, andwherein said glycol is ethylene glycol..Iaddend. .Iadd.29. A processaccording to claim 28, wherein said polyester is prepared utilizing anesterification stage and a condensation stage, which further comprisesadding said phosphorus compound during said esterification stage, andsaid antimony compound during said condensation stage..Iaddend..Iadd.30. A process according to claim 28, which further comprisesforming said polyester into a container..Iaddend. .Iadd.31. A processaccording to claim 29, which further comprises forming said polyesterinto a container, and wherein the amount of elemental antimony in saidantimony compound ranges from about 120 to about 210 parts of antimonyper million parts by weight of said polyester, and wherein the amount ofsaid elemental cobalt in said cobalt compound ranges from about 8 toabout 20 parts by weight per million parts by weight of saidpolyester..Iaddend. .Iadd.32. A process according to claim 30, whereinsaid container is a bottle..Iaddend. .Iadd.33. A process as specified inclaim 23, wherein said dicarboxylic acid is terephthalic acid, andwherein said glycol is ethylene glycol..Iaddend. .Iadd.34. The polyestermade by the process specified in claim 23..Iaddend. .Iadd.35. Thepolyester made by the process specified in claim 33..Iaddend.